Sampling and handling of mineral specimens



Dec. 15, 1953 F. H. BAlLLY SAMPLING AND HANDLING OF MINERAL SPECIMENSFiled April 25, 1949 INVENTOR. FL ORENT H. BA/LLY BY jaw Z4:

A T TORNEY Patented Dec. 15, 1953 OFFICE SAMPLING AND HANDLING OFIWINERAL SPECIMENS Florentv H. Bailly, Pasadena, Calif.

Application April 25, 1949, Serial No. 89,381

8' Glaims'.

This invention relates to sampling and testing methods and moreparticularly to such methods as employed in mineralogical analysis. Atypical field for the application of the present invention is in thesampling and testing of core samples or chip samples from oil and gasand other types of wells. Although not so limited, the'invention isdescribed with respect to this use.

Indrilling oil, gas and other types of wells, it is'conventionalpractice to take samples of the strata through which the drill bit ispassing; these samples,- depending" upon the type of drill equipment,are known as core samples or chip samples. By analyzing the same withrespect to permeability; porosity, saturation, interstitial water, etc.a great" deal can be learned regarding the nature of the particularstrata or horizon from which the core was taken. These several tests aregenerally included in the generic term core analysis which term willbeused throughout the present specification. Thepractice of coresampling not only allows the characteristicsof. a particular well boreto. be valued.

but, when combined with the same. procedures in adjacent and distant.wells provides a valuable aid in mapping the sub-surface geology of theregion.

The constantaimin ohtainingcore samplesfor. subsequent core analysis isto employ methods and techniques in the field that will ensure to thegreatest possible extent that the core as it reaches the laboratory foranalysis will be possessed of its original properties. It isevident thatany intervening loss or increase in moisture content or loss in oilcontent as well as any physical changes due to deterioration orinordinant temperature.

changes will result in erroneous interpretation of the characteristicsof the sub-surface strata from which the core was taken. The presentinvention is directed in part to improved techniques for core samplingto increase the reliability of data obtainable therefrom.

Present methods of core sampling are many and varies. In general thesemethods consist of enclosing the sample in a moisture resistant wrapper.or immersing the same in a heavy fiuid medium, say motor oil and sealingthe thus encased'core in an air tight container. Such methods do notentirely prevent sample alteration due to atmospheric changes intransportation. Particularly this so where the samples are shipped longdistances by air express or Where the atmospheric conditions at thelaboratory vary'markedly from those prevailing at the drilling site.Changes in temperature and pressure induce The physical structure of thecore may be altered if the method of obtaining it requires that it befrozen. Such a method is presently being practiced. Where the sample isimmersed in a heavy oil medium, it is impossible thereafter to determinethe hydrocarbon-water ratio thereof.

In accordance with the method of the present invention the core sample,chip sample or other mineralogical sample is cast into a chemically andphysically inert material which prevents any alteration in the sampleduring the period of transit from the site to the laboratory. To thesample itself as well as to the fluids contained therein the importanceof physical inertness of the casting material is emphasized by theforegoing discussion of changes occurring due to fluctuations inatmospheric temperatures and pressure. When the core sample is encasedin the physically inert materials such changes cannot affect it. Theproperties and characteristics of an ideal casting material inaccordance with the invention are as follows:

1. Complete, chemical inactivity with respect to sands, shales, clay,minerals, salts, brines, lime, crude oil, hydrocarbon and other gases,etc. normally encountered in drilling or mineralogical exploration work.

2. Physical resistance with respect to changes in atmosphericconditions. This requires that the materialpossess a certain amount ofresiliency to relieve stresses caused by volume changes of fluids andgases within the sample and that the material. be non-absorbent andnon-adsorbent to sample gases.

3. The material must be capable of shaping itself to the contours of thesample under ambient conditions of pressure existing in the field.

4. The material must adapt itself to handling both in the field and inthe laboratory.

A material possessing most closely the ideal characteristics outlinedabove was found to be a thermo setting plastic comprising an alkydpolyester-styrene copolymer. Other materials will fulfill theseconditions to a degree but none have been found which are superior tothe co-polymer mentioned. However, the invention is not limited to theuse of this particular plastic since others may be found in the futurewhich will satisfy the demands of the method of the invention to thesameorgreater degree than above mentioned material.

The method of the invention, so far as it pertains to obtaining samplesfrom the field is described in conjunction with the accompanying drawingin which:

Fig. 1 is an elevation partly in section showing the method of casting acore sample in the plastic;

Fig. 2 is a sectional elevation showing the encased sample ready forshipment;

Fig. 3 is a section taken on a line 33 of Fig. 2; and

Fig. 4 is a sectional elevation of the sample ready for laboratory test.

In obtaining core samples at a well, a core barrel is included in thedrilling string so that a cylindrical sample of, say ten feet in lengthand an inch or more in diameter is obtained from the well when the drillpipe is removed therefrom. At the surface the contents of the corebarrel are emptied into horizontal core trays. A suitable sample, orsamples, is selected and excess drilling mud removed therefrom. To thispoint the method of the invention is in accordance with conventionalpractice. According to preferred practice of the invention, the specificsample to go through all the laboratory tests is selected and cut to thedesired shape at the drill rig. One method of cutting the sample is witha double diamond saw by means of which a cube of rock of predeterminedsize and regular dimensions can be obtained.

Variations in the above procedures might include lowering thetemperature of the core sample so as to decrease the rate of evaporationof the oil or water content. The sample may be cut by any means and neednot be a cube although this form is preferred since it permitssubsequent measurement of permeability in three directions.

Referring to Fig. 1 the cut sample is iden tified by suitable marking asl23-l, shown in the drawing, and is inserted in a cylindrical, open toptube I2 containing a layer it of liquid plastic. Additional plastic ispoured over and around the sample ll! until it is completely encasedtherein. Thereafter a cover M is placed on the tube which is then readyfor shipment to the laboratory. I

Tube l2 may be made of substantially any material which will withstandthe temperature of the casting plastic during polymerization thereof. Athermo-plastic transparent plastic is preferred since it permitsobservation of the core at all times and since it is light and thusholds shipping weight to a minimum. An acetate-butyrate plastic is anexample or" a satisfactory material for this purpose.

When the sample arrives at the laboratory, tube [2 is removed therefromas shown in Fig. 4. A series of novel testing methods, made possible bythe plastic jacket l3 around the core, are hereinafter described.

Several considerations are of importance in selecting the conditionsunder which the core sample is cast in the plastic jacket. Ordinarily nosteps need be taken to protect the sample from ambient conditions oftemperature and pressure although this may be done if deemed desirable.Of more importance are such factors as gell time of the plastic coatingand the temperature rise in the plastic while gelling. The particulartype of plastic found to be most suited to the instant application, i.e. the copolymer of an alkyd polyester and styrene, is obtainablecommercially as a mixture or" the monomers. Upon the addition of asuitable catalyst, say a hydrocarbon peroxide or other peroxide, and anaccelerator, say cobalt naphthenate, copolymerization sets in and theplastic will gell. The gell time, i. e. the time it takes the plastic toset, is of particular important whereas the relatively longer timerequired for the plastie to reach its stable state is of little or noimportance.

The gell time of the plastic is a function of the amount of catalyst andaccelerator added as well as the ambient temperature and may range fromas little as four minutes to as high as several hours. It is importantto the practice of the present method that the gell time be establishedat a minimum consistent with other related factors of importance.

Although the catalyst and accelerator are added in the field a certainamount of time is required to perform the operations necessary to castthe sample. The gell time should be sufficiently long to permit of theseoperations. Additionally, if the gell time is too short stresses andstrains will occur which may produce cracking of the casting. Onefurther factor to be considered is the temperature rise in the plasticattendant upon the exothermic polymerization reaction. To preserve thesample in the best possible condition the temperature rise should beheld to less than 20 F. This constitutes another limitation on thepracticable minimum gell time since the temperature rise is inverselyproportional to gell time. All of these factors dictate the type ofplastics suitable for the practice of the invention as well as theamounts of catalyst and accelerator which should be used.

The effects of catalyst and accelerator on a commercially availablemixture of alkyd polyester and styrene monomers is illustrated in thefollowing tables. The catalyst employed in every case was a commerciallyavailable hydrocarbon peroxide and the accelerator was cobaltnaphthanate.

TABLE I Effect of accelerator concentration on setting time PercentPercent Setting Temperature Vol. of Monomer gggi Time in Rise inVolt-Hue Volumg Minutes Degrees F.

4 4 39 between 5-10. 4 1 27 Do. 4 2 9 Do. 4 4 4 40.

TABLE II Effect of catalyst on setting time Percent ACOGL Setting Time(in 62 32? minutes) Percent Cagil yst Vol. of Monomer y Volume Fromthese data it is evident that at least 1% by volume of catalyst shouldbe employed where 1% 0f accelerator is used. No definite limits can beestablished for catalyst and accelerator concentrations since" theireffects are to a certain extent overlapping. In fact the reaction may,if desired, be carried out in the absence of an accelerator.Additionally, the gell time is further effected by prevailingtemperatures and particularly by the temperature of the core. Moreover,the particular plastic, as well as the type of catalyst and acceleratorused in each applica-- tion will result in variations.

However, certain criteria can be established whereby anyone skilled intheart can select the proper amount of catalyst or the proper amounts ofcatalyst and accelerator to satisfy these criteria. Thus the temperaturerise in the body of plastic consequent upon exothermic reaction thereinshould be kept as low as possible and preferably below F. At the sametime the setting time should be held at a minimum consistent with theforegoing temperature limitation, required period of use (in workablestate) and a resultant structure free of cracks or fissures. In general,setting times of from approximately 8 to minutes have been foundsatisfactory in practice.

To establish the advantage of the sampling method of the invention overprior practices, a series of core samples were taken in horizontallycontiguous pairs. One sample of each pair was handled according toconventional practice by wrapping it in a moisture proof foil andsealing the wrapped sample in an air tight container. The other sampleof each pair was cast in plastic in the manner herein described. Thesamples of each pair were then shipped together to the laboratory andtheir moisture contents were determined. The results of this test areshown in Table III.

TABLE 111 Water Content grams/ grains of core ;;g'

sample PlasticCast.

Foil Wrapped Plastic Cast Percent i; 861 5. 152 6. 6 7. 994 8. 1. 7 7.481 7. 618 I 8 2. 953 3. 034 2; 7 3. 240 3. 465 9 2. 43s 2. 928 20. of4'. 907 5. 097 3: 9 6. 389 6. 482. L5 6 275 6. 836 8. 9

From these results it is evident that the method of the inventionimproves the accuracy of the data obtainable: from core samples. Theconventional method is subject to errors of from 1.5 to 20% which areavoided. by application of my method.

Another aspect of the present invention resides in improved laboratorytechniques made possible by the application of the above describedsampling method. Improvements in laboratory handling are directedprimarily to core analysis although similar practices may be applicablein other mineralogical testing procedures. As iii-- dicated above thecore samples can. be se-cal-led chip samples which are frequentlyobtained by cable tool drilling rather than rotary drillingand arebrought to the surface in a bailer rather than in a core barrel.

The presently practiced procedure for obtaining core samples isdescribed above. With respect" to handling these samples upon arrival atthe laboratory, they are: customarily un rugged samples.

wrapped and removed from the can, out into sub-sample size and weighedin an extraction thimble. Water is removed quantitatively in an ASTMwater determination apparatus and hydrocarbons are removed by Soxhletextraction for a period of several hours, say 12 to 18 hours. Water andhydrocarbon contents are calculated from weight differences of thesample before and after such treatment. The thus treated sample is thenrun through a pcrosimeter to determine porosity. If the sample happensto be friable as is the case of unconsolidated sands, it is necessary atthis stage tocoat it with a cellulose acetate or similar film to hold ittogether. If the sample is extremely friable the film of celluloseacetate is insuificientto hold it together through subsequentpermeability tests. Further, in the case of small or irregular samples,they must be set in optical pitch to adapt them to the permeabilityapparatus. The foregoing constitutes the usual complement of coreanalysis tests although other tests are often required if the sample atthis stage is still in condition to underg0 such additional tests. Inany case it is neces-' sary throughout the analysis to exercise judgmentas to whether subsequent tests in the serieswill destroy the sampleunless some special procedure is used to protect it.

I have described in considerable detail above, my new method ofobtaining core samples in the field. By practicing this method the testprocedures at the laboratory become very simple and are standard for anytype or sample, 1. e. unconsolidated and friable sands as well as moreAs previously described, the samples are cut at the site to the correctsize for testing and are received in the laboratory completely encasedin a jacket of transparent plastic. At the laboratory several holes aredrilled in two opposite faces of the jacket sample toallow entry andexit of fluid. A sample prepared for laboratory testing is shown in Fig.4. The sample comprises core sample It! cast in plastic jacket l3,container [2 having been removed preparatory to the testing operations.A series of holes H, I7, is are drilled through the plastic jacket atone end and a like number of holes 19, 20', 2| are drilled through thejacket at the opposite end of the sample. Thus prepared, the sample maybe subjected to repeated laboratory testing without fear of damage andwithout requiring. any additional protective measures.

By reason of the plastic jacket, I am enabled to employ improved testprocedures not heretoforev possible, and which greatly reduce the timerequired for obtaining a given series of test values. In accordance withthe improved procedure, the sample, prepared in the manner illustratedin- Fig. 4', is weighed once and placed in apressure washer. A suitablesolvent, as for example hexane or toluene, is forced through the sampleunder pressure for a few minutes.- This treatment removes the water andoil omen-- 1 titatively, the water being recovered in a separatereceiver for quantitative measurement and the solvent containing the oilbeing recovered separately for quantitative measurement of oil content.-This pressure washing procedure which may be: carried out in 15 minutesor less re-' places the presently used ASTM water deter mination methodand Sox hlet extraction which together take from 12" to 20 hours.Further, pressure washing made possible only because the sample isjacketed and hence is not subject- 7 to disintegration and solvent flowthrough thesample is confined between the inlet and outlet holes.

Subsequently, porosity and permeability measurements are made withexactly the same technique on all samples whether they be hard, soft,large, small or irregular because the external plastic jacket is ofuniform size and shape. No special precautions need be taken for friableor other unusual samples. Throughout this procedure the identity of thesample cannot possibly be lost as the number thereof is marked on thesample prior to casting and is observable through the transparentplastic until such time as the sample itself is destroyed. Further, evenafter undergoing the porosity and permeability tests the sample remainsin excellent condition for any or all of the subsequent special testswhich are frequently required as for example, interstitial water, andformation resistivity.

The methods of the invention possess a great number of advantages overthe presently practiced methods. A few of these advantages are listed:

1. There is no loss of oil Or water from the original sample duringshipment and storage by evaporation and condensation since the plasticjacket fits exactly the outer contour of the sample. The sample retainsits original properties to a greater degree than heretofore possiblesince it is exposed to the air only once at the well and thereafterremains encased in plastic throughout its entire progress through thelaboratory.

2. The jacketed sample is much lighter and less bulky to ship than thecanned or bottled samples. This is of particular benefit when thesamples are to be shipped by air express for corn siderable distances.The sample is suitable for all laboratory operations with a minimum ofeffort regardless of the fact that its physical properties may make itvery difiicult if not impossible to handle by present techniques. Thetesting time is materially decreased from an average of about hours byconventional methods to about one hour by the method of the invention.This becomes important when the completion of a well depends on resultsfrom the core laboratory.

3. Any test which is suspected of inaccuracy can be duplicated anynumber of times without risk of the sample deteriorating or fallingapart.

4. Standarization of the sampling method and testing procedures allowsthe same quality of results to be obtained in the laboratory for alltypes of samples with personnel of lower training level.

Many other advantages of the invention could be set forth, the foregoingbeing sufficient to show the benefits to be gained by practice of theinvention. In essence, the invention contemplates a sampling methodwhereby rock samples are cast in plastic as quickly as possible afterthey are recovered and are retained, as thus encased, throughout therest of their useful existence. All resuired laboratory tests are madeon the sample while still encased in the plastic by the simple expedientof drilling a number of holes through opposite faces of the plastic intothe rock sample. Any type of test may then be carried on withoutdeparting from the scope of the invention. Similarly, any type ofplastic which meets to a satisfactory degree the conditions herein setforth may be employed to encase the samples. The particular plasticreferred to in the foregoing description respresents the presentlypreferred plastic, although superior plastics may be discovered at alater date. The invention is not limited to the type of plasticemployed.

These and other modifications of the invention may occur to thoseskilled in the art without departing from the scope thereof.

I claim:

1. A method for treating a mineral sample which comprises completelysealing the sample shortly after its recovery by placing the sample in aliquid plastic bath and solidifying the bath around the sample to forman impervious plastic case, making holes through the plastic case onopposite sides of the sample, and forcing a fluid through the holes andthe sample enclosed in the case.

2. A method for treating a mineral sample which comprises completelysealing the sample shortly after its recovery by placing the sample in aliquid plastic bath and solidifying the bath around the sample to forman impervious plastic case, making holes through the plastic case onopposite sides of the sample, and forcing a solvent through the holesand the sample enclosed in the case to remove constituents of the samplewhich are soluble in the solvent.

3. A method for treating a mineral sample which comprises freezing thesample shortly after.

its recovery, and, while still frozen, completely sealing the sample byplacing the sample in a liquid plastic bath and solidifying thebatharound the sample to form an impervious plastic, case, making holesthrough the plastic case on opposite sides of the sample, and forcing afluid through the holes and the sample enclosed in the case.

i. A method for treating a mineral sample which comprises sizing thesample to desired dimensions, completely sealing the sample in a liquidplastic bath and solidifying the bath around the sample to form animpervious plastic case,

making holes through the plastic case on opposite sides of the sample,and forcing a fluid through the holes and the sample enclosed in thecase.

5. A method. for treating a mineral sample which comprises sizing thesample to the shape of a right cylinder of desired dimensions,completely sealing the sample in a liquid plastic bath and solidifyingthe bath around the sample to form an impervious plastic case, makingholes through the plastic case on opposite sides of the sample, andforcing a fluid through the holes and the sample enclosed in the case.

6. A method for determining the porosity of a mineral sample whichcomprises completely sealing the sample shortly after its recovery byplacing the sample in a liquid plastic bath and solidifying the batharound the sample to form an impervious plastic case, making holesthrough the plastic case on opposite sides of the sample. forcing afluid through the holes and the sample, and determining the porosity ofthe sample from the rate of fluid flow.

'7. A method for treating a mineral sample which comprises marking thesample with an identifying legend, completely sealing the marked sampleshortly after its recovery by placing the sample in a bath of atranparent liquid plastic and solidifying the bath around the sample toform a transparent impervious plastic case, making holes through theplastic case on opposite sides of the sample, and forcing a fluidthrough the holes and the sample enclosed in the case.

8. A method for testing a core sample containing hydrocarbons whichcomprises sizing the sample to desired dimensions, completely sealingthe sample in a liquid plastic bath and solidify:

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,588,164.- Brunner June 8, 1926 2,192,525 Rosaire et al Mar.5, 1940 Number 10 Name Date Bays Aug. 18, 1942 Homer Sept. 29, 1942Gerhart Nov. 3, 19 12 Sweeney Sept. 21, 1948 Reichertz Jan. 23, 1951Wisenbaker Nov. 11, 1952 OTHER REFERENCES 10 Bulletin R. I. 4004 ofBureau of Mines, Dec.

1946, page 3.

